The present invention relates to a hydraulic tool, more precisely relates to a hydraulic tool, in which a piston is reciprocally moved by a constant pressure pump and a constant volume pump.
Various types of hydraulic tools are used for connecting and cutting wires. A constant pressure pump and a constant volume pump have been used as pressure sources of the hydraulic tools. In the conventional hydraulic tools, the constant pressure pump or the constant volume pump is used as the pressure source.
However, manufacturing cost for manufacturing the both types of tools must be high. Further, in the case of selectively using the constant pressure pump and the constant volume pump, two types of the hydraulic tools must be prepared.
To solve the problems, a hydraulic tool capable of employing the constant pressure pump and the constant volume pump was provided in the constant pressure pump and the constant volume pumps as set forth in U.S. Pat. No. 5,778,755. In the hydraulic tool, a spool valve is opened and closed by an adjustment shaft and a seal nut so as to selectively use the constant pressure pump and the constant volume pump as the pressure source.
However, in the hydraulic tool of said U.S. patent, two adjustment screws are alternately and evenly tightened and loosened so as to change the pressure source. Therefore, changing the pressure source or the pump is troublesome. After the adjustment shaft is positioned by the seal nut, the seal nut is sometimes loosened, so that the position of the adjustment shaft is shifted. Further, an inside of the tool cannot be seen, so the position of the adjustment shaft should be indirectly known on the basis of a projected length of the adjustment shaft, which is projected from an end of a body of the tool, only. Furthermore, in the case of employing the constant pressure pump, the adjustment shaft is projected from the body much longer, so the adjustment shaft is apt to collide with other members and be damaged.
An object of the present invention is to provide a hydraulic tool capable of employing a constant pressure pump and a constant volume pump, easily switching the pumps, and correctly setting a switching position.
To achieve the object, the hydraulic tool of the present invention comprises:
a main body section including a cylinder and a piston;
a head section being attached to a front part of the cylinder, the head section including a movable part which is pushed by the piston, wherein the piston is capable of rotating about an axial line of the cylinder with the movable part;
a control section being provided to a rear part of the cylinder, the control section including oil paths, which connect the cylinder to a pressure source, and a switching valve, which is actuated by operating a handle so as to control an oil in the oil paths;
a piston valve being provided to the piston, the piston valve reciprocally moving in the axial.direction of the cylinder so as to control communication between a first cylinder chamber, which is provided on a front side of the piston, and a second cylinder chamber, which is provided on a rear side of the piston;
a concave being provided in a bottom face of the cylinder, the concave escaping an end of the piston valve from a position at which the end of the piston valve contacts a bottom face of the cylinder, and shutting off the communication between the first cylinder chamber and the second cylinder chamber when the piston valve moves toward the concave and the piston contacts the bottom face of the cylinder; and
a projection being provided at a position different from the concave in the bottom face of the cylinder, the projection making the end of the piston valve contact the bottom face of the cylinder and allowing the communication between the first chamber and the second cylinder chamber when the piston valve moves toward the projection and the piston contacts the.bottom face of the cylinder.
The hydraulic tool may further comprise a pair of seal heads being respectively provided to one end of the piston valve, which is located on the first chamber side, and the other end thereof, which is located on the second chamber side, the seal heads contacting a side face of the piston so as to shut off an oil path communication between the first chamber of the piston to the second chamber thereof.
In the hydraulic tool, a pair of the piston valves may be symmetrically provided with respect to a center of the cylinder, the concaves for accommodating the seal heads are formed in the bottom face of the cylinder.
The hydraulic tool may further comprise a head holder being provided to a cylinder head which is provided to the front part of the cylinder, the head holder holding the head section in a first state, in which the end of the piston valve is located in the concave, and a second state, in which the end of the piston valve contacts the projection.
The hydraulic tool may further comprises a relief valve being provided to the switching valve, wherein the oil, which has been introduced into an IN-port of the control section, is returned to an OUT-port thereof via the switching valve when the piston is pushed by the oil and oil pressure in the second chamber reaches prescribed pressure.
In the hydraulic tool of the present invention, the end of the piston valve can be moved between a position, at which the end of the piston valve is located in the concave of the cylinder, and another position, at which the end of the piston valve contacts the projection of the cylinder, by rotating the head section with respect to the cylinder. Namely, the pressure sources, which are a constant pressure source and a constant volume source, can be easily exchanged. Switching actions for exchanging the pressure source is the rotation of the head section, so reliability of the actions can be higher. Further, the positions for switching the pressure source can be easily visually known.